Iron alloy



. Patented Sept. 24, 1929 UNITED STATES PATENT OFFICE ALAN r. HILTON, orANSONIA, CONNECTICUT, ASSIGNOR TO FARREL-BIRMINGHAM COMPANY,INGORPORATED, or ANSONIA, CONNECTICUT IRON ALLOY No Drawing.

The present invention relates to an improvement in the manufacture ofcast iron, or ferrous alloys having the chemical characteristics of castiron, that is, which have carbon in excess of 2.25%. The cast ironembodying my invention may be in theform of gray iron, or chilled castiron or acid resisting iron and is particularly useful for themanufacture of chilled rolls for rolling 1o mills and similar articleswhich are subjected to heavy strains or loads, and to sudden changes oftemperature over a wide range. Such rolls must have a hard surface toresist the Wear to which they are subjected, i5 and have great strength,particularly when they are of considerable length and diameter. Thetendency inmodern rolling mill practice is towards increased productionwith the same amount, or even a less amount of equipment, throughincreased speed on the part of the mill rolls, and greater reduction ineach pass. At the same time, eiforts are being made to reduce powerlosses through friction, particularly in the bearings of the mills, andas a result of this effort there has been created a demand for rollshaving smaller necks than those heretofore used. For these reasons,together with the fact that the rolls of a mill are being continuallysubjected to increased stresses, strains, shocks and vibrations as theoutput of the mills is stepped up, and the fact that mill rolls muststand up under peculiarly rough usage, the metal of which the rolls arecomposed must have extraordinary strength, toughness and durability,Without sacrificing those characteristics of the roll surface which arere quired for the most satisfactory results on the product of the mill,and further Without prejudicially affecting the cost of the roll or thefacility with which it can be manufactured. Such rolls can be made ofsteel but cast iron is much more desirable as the cost of finished rollsmay be anywhere from a half to a fifth of the cost of steel rolls of thesame dimensions. However it has been found in the past that cast ironrolls of large dimensions frequently break in service, or crack or.split. This has been thought to be due to the loads to which they aresubjected til Application filed January 31, 1928. Serial No. 250 958.

and attempts have been made to overcome this by increasing the thicknessin the case of hollow rolls or by strengthening the material m the caseof solid rolls, or by usin steel. b

I have discovered however that by using a combination of proper amountsof certain alloying elements in certain definite proportions, a castiron alloy is produced having entirely novel characteristics and at acost only slightly in excess of ordinary cast iron and that chilledrolls and other similar articles subjected to heat and stresses and madefrom my novel cast iron are much stronger and more durable and are notsubject to the defects heretofore commonly observed in such rolls.

The invention is based in part on the discovery that the breakage ofchilled rolls is not ordinarily due to the stresses to which they aresubjected by their loads but is due to the different rate of expansionof the ch1lled and gray iron (unchilled) portions; and in part to thediscovery that the pres ence of certain alloying elements tends to varythe co-eliicients of expansion of the chilled iron and the gray ironportions respectlvely, and also the distribution of heat throughout themass can be thereby varied so that it will not set up so great stressesin the article.

In practice, I find that small amounts of copper in the presence ofsmall but sufiicient quantities of molybdenum gives to the cast iron thecharacteristics required and that the hardness required can be attainedby the use of chromium in quantities determined bv the use to Which theroll is to be put, Without destroying the effects of the cop er andmolybdenum. The depth of chill required can be regulated by the amountof silicon or' other suitable elements, which counteract the tendency ofthe copper to reduce the depth of chill and by the proper balancing ofthe several elements, as will be apparent to those skilled in the art.Manganese, sulphur and phosphorus will also be present in quantitiesaccording to the uses to which the finished material is to be put, itbeing understood ment, but'that in the presence of sulphur depending onthe ratio of the two it tends to soften the product.

In forming the alloy and casting the same, the more or less usualprocess used in the production of iron for casting is not undulycomplicated. The charge made up as usual of pig iron and scrap, togetherwith the alloy additions, including silicon, is melted in a suitablefurnace, or added in the ladle.

The cast iron embodying my invention in its broad aspects containsfcarbon, morethan 2.25%; copper, from 0.25 to 2.00% molybdenum, from 0.10to 2.00%; chromium, from 0.25 to 3.50%; silicon, not less than 0.25%;sulphur, from 0.02 to 0.20% manganese, from .10 to 3.00%; the balance tomake up 100% being of iron except for usual impurities. The addition ofsmall amounts of other alloying elements may perhaps be made withoutaffecting the essential qualities of the product.

For chilled rolls the proportions may be within the following ranges:carbon, more than 2.25%; copper, from 0.25 to 1.00%; molybdenum, from.10 to .75%; silicon, more than 25%; sulphur, from .02 to .18%, with. orwithout chromium in quantities up to 2.50% depending on the propertiesrequired, the balance to make up 100% being iron except for usualimpurities.

My preferred formula for chilled rolls for hot metal work is as follows:

Percent Carbon 3.00 Copper 0.50 Molybdenum 0.50 Chromium 1.50 Silicon1.25 Sulphur 0.07 Manganese 0.20

A suitable composition for gray iron is as follows:

Per cent Carbon 3.50 Copper 0.75 Molybdenum .50 Chromium 2.00 Silicon2.25 Sulphur .8.18 Manganese A03.00

A suitable composition for acid resisting iron 13 as follows Per centCarbon 3.50 Copper .75 Molybdenum .50 Chromium 3.00 Sulphur .18 Silicon3.25 Manganese .40-300 It is manifest that various changes in thesecompositions, such, for example, as the use of one per cent of chromiuminstead of two per cent in the gray iron composition, fall within thelimits hereinbcfore given.

The herein described compositions while having the desired physicalcharacteristics can be made at relatively low cost since copper is avery cheap alloying element and the amount of molybdenum required issmall, the result being that the final cost even when chromium is usedis exceedingly low considering the qualities of the articles produced.

I believe myself to be the first to recognize the fact that by the useof certain alloying elements and particularly those mentioned herein itis possible to control and regulate the thermal effects and propertiesof articles, especially chilled rolls which are subjected to heavy loadsand changes of temperature over wide ranges, and thereby to overcome thedefects which have been erroneously thought in the past to have been dueto insuffic ient strength.

I do not claim herein a cast iron alloy containing coper in effectiveamount and more than 2.25% carbon, together with from 0.15% to 2%molybdenum, as claimed in my .livisional application, Serial No.382,837, filed August 1st, 1929.

What I claim is 1. A cast iron alloy containing carbon more than 2.25%,copper from .25% to 2%, molybdenum .10% to 2% and chromium in effectiveamount up to 3.50%.

2. A cast iron alloy containing carbon more than 2.25%, copper from 25%to 1%, molybdenum from 10% to .7 5%, and chromium in effective amount upto 2.50%.

3. A cast iron alloy chilled roll containing carbon 3%, copper .50%,molybdenum 0.50% and chromium 1.50%.

ft. A cast iron alloy chilled roll containing carbon 3%, copper .50%,molybdenum 0.50%, chromium 1.50% and silicon 1.25%.

In witness whereof, I have hereunto set my hand this 28th dayof'January, 1928.

ALAN F. HILTON.

